The Rail Accident Investigation Branch (RAIB) has released a safety digest after an investigation into an incident of overspeeding at Cambridge Junction near Hitchin in Hertfordshire.

On 11th December 2025, the 10:12 London King’s Cross to Ely travelling at excessive speed crossed Cambridge Junction, which is where trains travelling north on the East Coast Main Line diverge from the line towards Cambridge. The train was routed to take the diverging route over the junction towards Cambridge, which required the train to pass over six sets of points and a switch diamond.

On the Cambridge line, the first two sets of points have a permanent speed restriction of 25 mph, while over the rest of the route, speed is restricted to 40 mph.

Instead of the mandatory 25 mph, the train began to cross the first two sets of points at 56 mph. As the train crossed the junction, it lurched sideways, and several passengers fell from their seats, and the standing passengers were thrown off balance. No passengers sustained injuries because of the incident, and neither the train nor the railway infrastructure was damaged.

The RAIB concluded that the driver expected the train to go via a flyover over the East Coast Main Line, which allows a higher speed on the route towards Cambridge; the information the signalling system provided to the driver did not change his expectation.

The train had been travelling at a reduced speed because a single yellow aspect signal was displayed by a preceding signal. When the next signal changed aspect, the train was over 500 metres from it, and the driver proceeded as if it was routed towards the flyover. Although the signal remained visible, it did not provide sufficient information to change the driver’s understanding of the route the train would take.

The driver was newly qualified and had only passed to drive unaccompanied 11 days previously. During their initial driver training, most of their in-cab experience was over routes south of Finsbury Park, but when driving with an instructor between London and Cambridge, they received limited experience of driving over all possible routes at Cambridge Junction.

Once drivers complete their training, in order to pass their initial competence assessment, Govia Thameslink Railway (GTR) evaluates them on their knowledge of all designated routes.

In its route risk assessment, GTR had not identified the risk of the junction indicator at this signal for the Cambridge line being misread by a driver. However, since the flyover opened, the level route across the was rarely used, with no passenger trains being timetabled over the route. During Monday to Friday in the two weeks before the incident, data showed fewer than four trains used this route each day.

The RAIB has reached the following conclusions in producing its safety digest:

• Drivers should maintain alertness when approaching junction signals to ensure that all the information the signals provide is acted upon.
• Drivers should not make assumptions about the route set ahead based on their previous experience with commonly set routes.
• Route risk assessments should identify junctions where there is a significant speed reduction on the diverging route, and drivers should be made aware of these locations.
• Infrastructure managers and train operating companies should recognise that overspeeding may occur, even when the point of divergence is very close to the junction signal.

A similar incident of overspeeding occurred at Grantham South Junction on 25th February 2025.